The invention relates generally to knee surgical techniques and, more particularly, to apparatus and method for resection of the knee joint for a knee prosthesis.
Replacement of a knee joint with a prosthesis involves a comprehensive surgical procedure, as is known to those skilled in the art. The surgical procedure is complicated by the fact that only a relatively small area of the patient's leg, namely the knee, is exposed during the operation. The remainder of the patient's leg, as well as most of his body, is covered with sterile drapes. The R.M.C..TM. Total Knee System technique manual published by Richards Manufacturing Company, Inc., 1450 Brooks Rd., Memphis, Tenn. 38116 illustrates this aspect of the surgical procedure. The surgical procedure is further complicated by the presence of the muscle and skin tissue which surrounds the knee joint.
Once the knee joint is exposed by known techniques, the distal femur and proximal tibia must be prepared to enable implantation of the prosthesis. Such preparation includes resection of the anterior and posterior distal femoral condyles, the proximal tibia, and the distal femur. In order to achieve proper stability of the knee prosthesis when implanted, the aforementioned resections must be accurately aligned relative to an imaginary axis extending through the hip joint, knee joint, and ankle joint.
It is necessary for the distal femoral condylar resections to be parallel to the proximal tibial resection when the knee is in flexion and for the proximal tibial resection when the knee is in extension. These "triplanar" resections should be made to provide equal flexion and extension gaps, i.e., the distance between the posterior femoral condylar resection and the proximal tibial resection with the knee in flexion (the flexion gap) should be equal to the distance between the distal femoral resection and the proximal tibial resection with the knee in extension (the extension gap). Furthermore, the resected proximal tibia and resected distal femur should be perpendicular to the above-referenced imaginary axis when the knee is extended.
The necessity of accurately making the triplanar resections has led to the development of relatively complicated instrumentation to aid the orthopedic surgeon. Illustrative of such instrumentation are the Howmedica.RTM. Universal.TM. Total Knee Instrument System as shown in the catalogue published by Howmedica, Inc., Orthopaedics Division, 359 Veterans Blvd., Rutherford, N.J. 07070 and the Insall/Burstein surgical instrument system as designed by John Insall, M.D. and Albert H. Burstein, Ph.D. and shown in the publication entitled "Knee Replacement Using the Insall/Burstein Total Condylar Knee System."
Although providing some guidance to the orthopedic surgeon, these prior instrument systems utilize long alignment rods which have proved to be less than satisfactory under sterile operating room conditions, as described previously. Furthermore, such instrument systems include numerous components which still require much manual manipulation and which are cumbersome to use.